Low back injuries account for more absence from work than any other disease and municipal employees are a high-risk group. A multidisciplinary team of researchers proposes to work closely with the Baltimore City Office of Occupational Medicine and Safety, with the goal of understanding and reducing low back injuries among Baltimore's 39,000 municipal employees. A case-control study will be conducted to accomplish the following specific aims: 1) to describe the nature, type, and circumstances of back injury; 2) to determine if worker characteristics, work patterns, hazardous exposures, materials handling practices, and personal and job stressors differ between cases and matched controls; and 3) to develop specific recommendations to reduce occupational low back injury based on the above findings. Data will be collected from injury incident reports, medical records, personnel records, site visits, and by means of in-person interviews of cases and controls. Cases will have sustained low back injury while at work; back pain must be acute in onset and result in restricted activity or lost work time. One control will be individually matched to each case on the basis of department, job, gender, and presence at work on the day the case was injured. A second control will be drawn from workers in all departments who have the same job classification. Personal interviews of cases and controls will be conducted within ten days of injury. In addition, site visits will be made to reconstruct the case's activity at the time of injury. Data will be analyzed according to univariate and multivariate methods for matched pairs. A conditional logistic regression model will also be utilized. The findings of this study should form the basis for planning effective interventions to reduce occupationally related lower back injuries.